Incoming is a packet monitor designed to monitor SYN packets. Machines receive SYN packets when a remote machine is trying to initiate a TCP connection.

When a machine is listening on a port, it replies the machine sending the SYN packet with an aknowledgement ( ACK ) request. If the machine is not listening on a particular port, then the machine will reply with a reset ( RST ) request.

Many crackers use the SYN scan technique to detect open ports. This helps the crackers easily detect the services running on a machine.

Incoming is a utility designed to closely monitor the SYN packets being received by a machine. This can be of great help to machines that act as servers on the internet, or machines that are directly connected to the internet through a broadband connection.